Thermosetting resin composition

ABSTRACT

A modified carbodiimide resin obtainable by reacting a carbodiimide resin comprising a repeating unit represented by the general formula: —(NCN—R 1 )— wherein R 1  represents a divalent organic group, with an aromatic diamine represented by the general formula: H 2 N—R 2 —NH 2  wherein R 2  represents a divalent organic group having a benzene ring, and a thermosetting resin composition comprising the modified carbodiimide resin and an epoxy resin.

BACKGROUND OF THE INVENTION

The present invention relates to a thermosetting resin composition. Inparticular, the present invention relates to a thermosetting resincomposition which is suitably used for protective layers, electricinsulation coatings and the like for electric appliances, electronicdevices and the like. The present invention also relates to a modifiedcarbodiimide resin which is suitably used as a component of theaforementioned thermosetting resin composition.

As such a thermosetting resin composition as mentioned above, there havebeen known, for example, thermosetting resin compositions containing oneor more kinds of organic polyisocyanates, one or more kinds of organicmonoisocyanates, one or more kinds of crosslinking agents having two ormore active hydrogen groups in a molecule thereof, and one or more kindsof catalysts promoting carbodiimidation of the isocyanates such as thosedescribed in Japanese Patent Publication No. 5-6564 (1993), andthermosetting resin compositions characterized in that they contain (A)a resin which is composed of a polycarbodiimide containing a repeatingunit represented by the general formula —N═C═N—R¹— wherein R¹ representsa divalent organic group, on which one or more kinds of compounds havinga group causing grafting reaction and a carboxylic acid anhydride groupare grafted, and (B) an epoxy compound such as those disclosed inJapanese Patent Application Laid-Open No. 8-81545 (1996).

However, an adhesive property and resistance to humidity after curing ofsuch thermosetting resin compositions as those disclosed in JapanesePatent Publication No. 5-6564 (1993) have room for improvement, thoughthey are excellent in heat resistance after curing. Further, suchthermosetting resin compositions as those disclosed in Japanese PatentApplication Laid-Open No. 8-81545 (1996) requires strict moisturecontent control because they have acid anhydride groups, anddisadvantageously takes a long period of time for the reaction with theepoxy resin.

SUMMARY OF THE INVENTION

The present invention has been accomplished to solve such problems ofthe prior art, and its object is to provide a thermosetting resincomposition which is excellent in an adhesive property, resistance tohumidity, and heat resistance after curing, and requires less labor forthe production process control.

The present inventors earnestly conducted investigations to achieve theaforementioned object, and as a result, found that a thermosetting resincomposition which is excellent in an adhesive property, resistance tohumidity and heat resistance can be obtained by mixing a carbodiimideresin modified with an aromatic diamine, and an epoxy resin, and curingthem. Based on this finding, the present invention has beenaccomplished.

Thus the present invention provides a thermosetting resin composition(also referred to as the thermosetting resin composition of the presentinvention hereinafter) which comprises:

a modified carbodiimide resin obtainable by reacting a carbodiimideresin comprising a repeating unit represented by the general formula:—(NCN—R¹)— wherein R¹ represents a divalent organic group, with anaromatic diamine represented by the general formula: H₂N—R²—NH₂ whereinR² represents a divalent organic group having a benzene ring, and

an epoxy resin.

In the thermosetting resin composition of the present invention, R¹ ispreferably an organic group derivable from an aromatic diisocyanate. Thearomatic diamine is preferably diaminodiphenyl sulfone ordiaminodiphenylmethane.

The epoxy resin is preferably a bisphenol epoxy resin or a novolak epoxyresin.

The present invention also provides the above modified carbodiimideresin usable for the thermosetting resin composition of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention will be described hereinafter.

(1) Modified Carbodiimide Resin

The modified carbodiimide resin can be obtained by reacting acarbodiimide resin and an aromatic diamine.

The carbodiimide resin is a resin containing a repeating unitrepresented by the general formula: —(NCN—R¹)— wherein R¹ represents adivalent organic group.

The carbodiimide resin can be produced by allowing an organicpolyisocyanate to react in the presence of a carbodiimidation catalystthat catalyzes carbodiimidation reaction of isocyanate groups accordingto a known method (see, for example, Japanese Patent ApplicationLaid-Open No. 8-81545(1996)).

Examples of the organic polyisocyanate include aromatic polyisocyanatesand aliphatic polyisocyanates. More specifically, there can be mentionedtolylene diisocyanate (in the present specification, it means2,4-tolylene diisocyanate, 2,6- tolylene diisocyanate, or a mixturethereof, and they are collectively referred to as TDI),4,4′,4″-triphenylmethylene triisocyanate,4,4,-dimethyldiphenylmethane-2,2′,5,5,-tetraisocyanate, xylenediisocyanate, hexamethylene-1,6-diisocyanate, lysine diisocyanate methylester, polymethylene polyphenyl isocyanate, hydrogenated methylenediphenyl isocyanate, m-phenylene diisocyanate,naphthylene-1,5-diisocyanate, 1-methoxyphenyl-2,4-diisocyanate,diphenylmethane-4,4′-diisocyanate (referred to as MDI), 4,4′-biphenylenediisocyanate, 3,3′-dimethoxy-4,4′-biphenyl diisocyanate,3,3′-dimethyl-4,4′-biphenyl diisocyanate,3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, isophorone diisocyanateand the like.

Preferred organic polyisocyanates are organic diisocyanates, andpreferred organic diisocyanates include, for instance, aromaticdiisocyanates. Specific examples thereof are TDI and MDI. These organicpolyisocyanates may be used alone or as a mixture of two or more kindsof them.

R¹ is specifically a divalent organic group derivable from theaforementioned organic polyisocyanates. R¹ may consist of a plurality ofkinds of groups, and in such a case, the bonding order of such groups isnot particularly limited. Preferably, R¹ is an organic group having thefollowing formula, which can be derived from TDI and MDI:

The average molecular weight of the carbodiimide resin used for thepresent invention is generally in the range of 200 to 50000, preferablyin the range of 500 to 20000.

The carbodiimide resin may be one synthesized by simultaneously usingorganic polyisocyanates and organic monoisocyanates in order to, forexample, control the molecular weight. As such organic monoisocyanates,there can be mentioned phenyl isocyanate, o-, m- or p-tolyl isocyanate,dimethylphenyl isocyanate, cyclohexyl isocyanate, methyl isocyanate,chlorophenyl isocyanate, trifluoromethylphenyl isocyanate, naphthylisocyanate and the like. As for the amount of the organic monoisocyanateto be used, while it may be selected depending on the desired physicalproperties, it is usually used in a stoichiometric ratio with respect tothe organic polyisocyanate, i.e., a ratio to isocyanate groups of theorganic polyisocyanate, of 0.01 to 0.3, preferably 0.02 to 0.2.

The aromatic diamine is represented by the general formula H₂N—R²—NH₂wherein R² is a divalent organic group having a benzene ring.

Examples of the aromatic diamine include diaminodiphenyl sulfone,diaminodiphenylmethane, diaminodiphenyl ether and the like. Preferredaromatic diamines are diaminodiphenyl sulfone, anddiaminodiphenylmethane.

The reaction of the carbodiimide resin and the aromatic diamine may beperformed by, for example, dissolving the carbodiimide resin in asolvent, adding the aromatic diamine to the solution, and mixing andheating the solution. As the solvent, any organic solvents dissolvingthe carbodiimide resin such as toluene, cyclohexanone, andtetrahydrofuran can be used. The reaction rate may be suitablycontrolled within a range up to the reflux temperature of the solventused.

The reaction may also be performed by adding the aromatic diamine to areaction mixture in which the carbodiimide resin has been synthesizedwithout separating the formed carbodiimide resin from the reactionmixture.

As for the ratio of the carbodiimide resin to the aromatic diamine,usually 0.01 to 1 mol. preferably 0.02 to 0.5 mol of the diamine is usedfor 1 equivalence of carbodiimide group.

Because the modified carbodiimide resin is usually deposited as powder,the formed modified carbodiimide resin can be collected by filtrationfrom the reaction mixture after the reaction, and dried to give themodified carbodiimide resin.

The modified carbodiimide resin obtained as described above isconsidered to have a partially guanidylated structure (guanidine group)represented by the following formula:

In the formula, R¹ and R² have the same meanings as defined above, andm, n, k and l are each an integer.

As seen from the aforementioned structure, the modified carbodiimideresin used for the present invention does not have any unstable groupssuch as acid anhydride groups, and therefore the production processcontrol for the thermosetting resin containing it is easy. Accordingly,the present invention also provides the modified carbodiimide resinmentioned above which is suitably usable for the thermosetting resincomposition.

(2) Epoxy Resin

The epoxy resin is not particularly limited so long as the modifiedcarbodiimide resin functions as its curing agent.

Examples of the epoxy resin include glycidyl ether epoxy resins(bisphenol epoxy resins, novolak epoxy resins, cresol novolak epoxyresins and the like), glycidyl ester epoxy resins, glycidylamine epoxyresins, alicyclic epoxy resins, heterocyclic epoxy resins, liquidrubber-modified epoxy resins and the like. Preferred epoxy resins arebisphenol epoxy resins and novolak epoxy resins. These epoxy resins areused alone or as a mixture of two or more kinds of them.

(3) Thermosetting Resin Composition

The thermosetting resin composition of the present invention can beobtained by mixing the modified carbodiimide resin and the epoxy resinexplained above.

While the mixing ratio of the modified carbodiimide resin and the epoxyresin may be suitably selected depending on the kind of the resins,purpose of the composition and the like, usually 1 to 400 parts byweight, preferably 5 to 200 parts by weight of the epoxy resin is usedfor 100 parts by weight of the modified carbodiimide resin.

The means for mixing is not particularly limited, but fusion kneading bya kneader or a hot mill, mixing in a suitable solvent inert to themodified carbodiimide resin and the epoxy resin and the like can beexemplified.

The thermosetting resin composition of the present invention may containvarious additives which have been used for conventional thermosettingresin compositions. As such additives, fiber reinforcing materials,powder or crystalline fillers (e.g., fused silica), pigments, curingcatalysts promoting curing by the reaction of the modified carbodiimideresin and the epoxy resin, and the like can be mentioned. Such variousadditives may either be simultaneously added upon the mixing mentionedabove, or added after the aforementioned mixing. They may also be addedto any one of the resins mentioned above before the mixing.

The thermosetting resin composition of the present invention may be usedin a ground state, if necessary. The various additives may be combinedafter the grinding.

The thermosetting resin composition of the present invention can beconverted to a final cured product by heating to a temperature in therange of, usually 80 to 200° C., preferably 120 to 200° C. A curedproduct in a desired shape can be obtained by performing the heating ina suitable mold under pressure.

This curing is considered to be caused by crosslinking obtained by thereaction between the guanidine groups present in the modifiedcarbodiimide resin and the epoxy groups, and the reaction between thecarbodiimide groups and the epoxy groups.

In the formula, R¹ and R² have the same meanings as defined above, R₃ isa divalent organic group, and x, y and z are each an integer.

According to the present invention, there are provided a thermosettingresin composition which is excellent in an adhesive property, resistanceto humidity, and heat resistance after curing, and a modifiedcarbodiimide resin suitably used for the composition. Further, becausethe thermosetting resin composition of the present invention does notcontain unstable reactive groups such as acid anhydride groups, itrequires less labor for the production process control.

EXAMPLES

The present invention will further be described with reference to thefollowing examples hereinafter.

Synthesis Example 1

MDI (60.0 g), phenyl isocyanate (PhNCO, 4.76 g), and toluene (250.0 g)were introduced into a 500-ml separable flask, and1-phenyl-3-methyl-3-phospholene-1-oxide (86.3 mg) as a carbodiimidationcatalyst was added thereto. The mixture was allowed to react underreflux for five hours to give Carbodiimide resin solution {circle around(1)}.

To 200 g of the above Carbodiimide resin solution {circle around (1)},diaminodiphenyl sulfone (DDS, 4.25g) was added. After they were allowedto react for five hours under reflux, pale white powder was produced.The powder was taken by filtration and dried to give Modifiedcarbodiimide resin powder {circle around (1)} (37.4 g). In the IRanalysis of this powder, absorption at 2150-2100 cm⁻¹ of carbodiimidegroup, and absorption at 1640 cm⁻¹ of guanidine group were confirmed.

Further, Modified carbodiimide resin powder {circle around (2)} (35.9 g)was obtained in the same manner as the synthesis of the above Modifiedcarbodiimide resin powder {circle around (1)}, except that 2.07 g of DDSwas added to 200 g of the above Carbodiimide resin solution {circlearound (1)}. In the IR analysis of this powder, absorption at 2150-2100cm⁻¹ of carbodiimide group, and absorption at 1640 cm⁻¹ of guanidinegroup were confirmed.

Synthesis Example 2

TDI (2,4-compound:2,6-compound=80:20, 34.9 g), PhNCO (4.78 g), andcyclohexanone (270.0 g) were introduced into a 500-ml separable flask,and 1-phenyl-3-methyl-3-phospholene-1-oxide (71.1 mg) as acarbodiimidation catalyst was added thereto. The mixture was allowed toreact at 120° C. for six hours to give Carbodiimide resin solution{circle around (2)}.

To 200 g of the above Carbodiimide resin solution {circle around (2)},DDS (1.79 g) was added. After they were allowed to react at 120° C. forsix hours, yellow powder was produced. The powder was taken byfiltration and dried to give Modified carbodiimide resin powder {circlearound (3)} (19.7 g). In the IR analysis of this powder, absorption at2140 cm⁻¹ of carbodiimide group, and absorption at 1650 cm⁻¹ guanidinegroup were confirmed.

Reference Example

Carbodiimide resin solution {circle around (1)}provided in SynthesisExample 1 was cooled to 10° C. to deposit a resin, and was filtered togive Carbodiimide resin powder {circle around (4)} with a yield of 95%.

Carbodiimide resin solution {circle around (2)} provided in SynthesisExample 2 was cooled to 10° C., and mixed with acetone as a poor solventto deposit a resin. However, it was obtained as a mass, and could not beobtained as powder.

Examples 1 to 4 and Comparative Examples 1 and 2

By using Carbodiimide resin powders {circle around (1)} to {circlearound (4)} obtained in Synthesis Examples 1 and 2 and ReferenceExample, the materials, i.e., epoxy resin, carbodiimide resin powder andfused silica, were mixed in the ratios represented in Table 1, andsubjected to fusion kneading in a hot mill. Subsequently, the mixtureswere cooled and ground to obtain powdered resin compositions.

By using the obtained powdered resin compositions, silicon chips weresealed by the transfer molding method to prepare flat package typesealed semiconductor devices as test pieces. These test pieces wereevaluated for solder heat resistance and resistance to humidity by thefollowing methods. The results are also shown in Table 1.

Evaluation 1. Solder Heat Resistance

Test pieces were placed under the conditions of 85° C. and 85% Rh for 72hours, and then dipped in a solder bath at 250° C. for 10 seconds. Thisprocedure was repeated twice. The results are represented as numbers ofthe test pieces generating cracks per 12 test pieces.

2. Resistance to Humidity

Test pieces were placed in saturated steam under the conditions of 121°C. and 2 atm for 100 hours, and leak current value of the test pieces(semiconductor package devices) was measured. Any test pieces thatexhibited a value higher by 5 times or more than that obtained beforethe test were considered defective, and the results are represents asthe numbers of defective test pieces per 12 test pieces.

TABLE 1 Composition and evaluation results Comparative Example example 12 3 4 1 2 <Composition> Epoxy resin Bisphenol A type 15 13 15 15 Novolaktype 13 13 Carbodiimide resin powder {circle around (1)} 10 12 {circlearound (2)} 12 {circle around (3)} 10 {circle around (4)} 10 12 Fusedsilica 75 75 75 75 75 75 <Evaluation> Solder heat 0/12 0/12 1/12 0/12 9/12 6/12 resistance Resistance to 0/12 1/12 0/12 0/12 10/12 9/12humidity Bisphenol A epoxy resin (epoxy equivalent: 190 g/eq) Novolakepoxy resin (epoxy equivalent: 180 g/eq)

As clearly seen from the results shown in Table 1, when the modifiedcarbodiimide resins of the present invention were used, excellent solderheat resistance and resistance to humidity could be obtained. Further,since solder heat resistance and resistance to humidity arecharacteristics influenced by an adhesive property, it was alsoconfirmed that they were excellent in the adhesive property.

What is claimed is:
 1. A thermosetting resin composition comprising: amodified carbodiimide resin obtained by reacting a carbodiimide resincomprising a repeating unit represented by the general formula:—(NCN—R¹)—, wherein R¹ represents a divalent organic group, with anaromatic diamine represented by the general formula: H₂N—R²—NH₂ whereinR² represents a divalent organic group having a benzene ring, and anepoxy resin.
 2. The thermosetting resin composition according to claim1, wherein R¹ is a group derived from an aromatic diisocyanate.
 3. Thethermosetting resin composition according to claim 1, wherein thearomatic diamine is diaminodiphenyl sulfone or diaminodiphenylmethane.4. The thermosetting resin composition according to claim 2, wherein thearomatic diamine is diaminodiphenyl sulfone or diaminodiphenylmethane.5. The thermosetting resin composition according to claim 1, wherein theepoxy resin is a bisphenol epoxy resin or a novolak epoxy resin.
 6. Thethermosetting resin composition according to claim 2, wherein the epoxyresin is a bisphenol epoxy resin or a novolak epoxy resin.
 7. Thethermosetting resin composition according to claim 3, wherein the epoxyresin is a bisphenol epoxy resin or a novolak epoxy resin.
 8. Thethermosetting resin composition according to claim 4, wherein the epoxyresin is a bisphenol epoxy resin or a novolak epoxy resin.